Managing jackknife enabling conditions during backing of a trailer by reducing speed of a vehicle backing the trailer

ABSTRACT

A vehicle comprises a trailer angle detection apparatus and a trailer backup control system. The trailer angle detection apparatus is configured for outputting hitch angle information generated as a function of an angle between the vehicle and a trailer towably attached thereto. The trailer backup control system includes a jackknife enabling condition detector and a jackknife counter-measures controller coupled to the trailer angle detection apparatus. The jackknife enabling condition detector is coupled to the trailer angle detection apparatus for receiving the hitch angle information therefrom and for determining if a jackknife enabling condition has been attained at a particular point in time during backing of the trailer by the vehicle. The jackknife counter-measures controller implements a vehicle speed reducing action in response to the jackknife enabling condition detector determining that the jackknife enabling condition has been attained at the particular point in time during backing of the trailer.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation-in-part application ofco-pending U.S. Non-provisional patent application which has Ser. No.13/336,060, which was filed Dec. 23, 2011, which is entitled “TrailerPath Curvature Control For Trailer Backup Assist”, which claims priorityfrom co-pending U.S. Provisional Patent Application which has Ser. No.61/477,132, which was filed Apr. 19, 2011, which is entitled “TrailerBackup Assist Curvature Control”, and both of which have a commonapplicant herewith and are being incorporated herein in their entiretyby reference.

FIELD OF THE DISCLOSURE

The disclosures made herein relate generally to driver assist and activesafety technologies in vehicles and, more particularly, to implementingjackknife detection and counter-measures during back-up of a trailer.

BACKGROUND

It is well known that backing up a vehicle with a trailer attached is adifficult task for many drivers. This is particularly true for driverswho are untrained at backing with trailers such as, for example, thosewho drive with an attached trailer on an infrequent basis (e.g., haverented a trailer, use a personal trailer on an infrequent basis, etc).One reason for such difficulty is that backing a vehicle with anattached trailer requires counter-steering that is opposite to normalsteering when backing the vehicle without a trailer attached and/orrequires braking to stabilize the vehicle-trailer combination before ajack-knife condition occurs. Another reason for such difficulty is thatsmall errors in steering while backing a vehicle with an attachedtrailer are amplified, thereby causing the trailer to depart from adesired path.

To assist the driver in steering a vehicle with trailer attached, atrailer backup assist system needs to know the driver's intention. Onecommon assumption with known trailer backup assist systems is that adriver of a vehicle with an attached trailer wants to back up straightand the system either implicitly or explicitly assumes a zero curvaturepath for the vehicle-trailer combination. Unfortunately most ofreal-world use cases of backing a trailer involve a curved path and,thus, assuming a path of zero curvature would significantly limitusefulness of the system. Some known systems assume that a path is knownfrom a map or path planner. To this end, some known trailer backupassist systems operate under a requirement that a trailer back-up pathis known before backing of the trailer commences such as, for example,from, a map or a path planning algorithm. Undesirably, suchimplementations of the trailer backup assist systems are known to have arelatively complex Human Machine Interface (HMI) to specify the path,obstacles and/or goal of the backup maneuver. Furthermore, such systemsalso require some way to determine how well the desired path is beingfollowed and to know when the desired goal, or stopping point andorientation, has been met, using approaches such as cameras, inertialnavigation, or high precision GPS. These requirements lead to arelatively complex and costly system.

As previously mentioned, one reason backing a trailer can prove to bedifficult is the need to control the vehicle in a manner that limits thepotential for a jack-knife condition to occur. A trailer has attained ajackknife condition when a hitch angle cannot be reduced (i.e., madeless acute) by application of a maximum steering input for the vehiclesuch as, for example, by moving steered front wheels of the vehicle to amaximum steered angle at a maximum rate of steering angle change. In thecase of the jackknife angle being achieved, the vehicle must be pulledforward to relieve the hitch angle in order to eliminate the jackknifecondition and, thus, allow the hitch angle to be controlled viamanipulation of the steered wheels of the vehicle. However, in additionto the jackknife condition creating the inconvenient situation where thevehicle must be pulled forward, it can also lead to damage to thevehicle and/or trailer if certain operating conditions of the vehiclerelating to its speed, engine torque, acceleration, and the like are notdetected and counteracted. For example, if the vehicle is travelling ata suitably high speed and/or subjected to a suitably high longitudinalacceleration when the jackknife condition is achieved, the relativemovement of the vehicle with respect to the trailer can lead to contactbetween the vehicle and trailer thereby damaging the trailer and/or thevehicle.

Therefore, an approach for detecting an actual or impending jackknifecondition for a trailer being backed by a vehicle (i.e., a jackknifeenabling condition) and thereafter implementing an action forsufficiently reducing a speed of a vehicle backing the trailer to causethe jackknife enabling condition to be prevented or alleviated and,optionally, implementing a vehicle speed dependent jackknife warningwould be beneficial, desirable and useful.

SUMMARY OF THE DISCLOSURE

Embodiments of the present invention are directed to assisting a driverwith backing a trailer attached to a vehicle in a manner that limits thepotential for or alleviates a jackknife condition between the vehicleand the trailer. More specifically, embodiments of the present inventionare directed to detecting an impending jackknife condition (i.e., ajackknife enabling condition) and correspondingly implementing one ormore vehicle speed reducing actions for alleviating the impendingjackknife condition. In some embodiments of the present invention, awarning (e.g., tactile, audible, visual and/or the like) can beimplemented in conjunction with the vehicle speed reducing action beingimplemented. Accordingly, embodiments of the present inventioncontribute to trailer backup assist functionality being implemented in amanner that is relatively simple, effective, and safe.

In one embodiment of the present invention, a method comprises one ormore data processing device accessing, from memory coupled to the atleast one data processing device, instructions causing the one or moredata processing devices to assess jackknife determining information fora vehicle and a trailer towably to the vehicle and the one or more dataprocessing devices accessing, from the memory, instructions causing theone or more data processing devices to implement a vehicle speedreducing action in response to the jackknife determining informationindicating that a jackknife enabling condition has been attained at aparticular point in time during backing of the trailer by the vehicle.

In another embodiment of the present invention, an electronic controlsystem has a set of instructions tangibly embodied on a non-transitoryprocessor-readable medium thereof. The set of instructions areaccessible from the non-transitory processor-readable medium by one ormore data processing devices of the electronic controller system forbeing interpreted thereby. The set of instructions is configured forcausing the one or more data processing devices to carry out operationsfor assessing jackknife determining information for a vehicle and atrailer towably to the vehicle and implementing a vehicle speed reducingaction in response to the jackknife determining information indicatingthat a jackknife enabling condition has been attained at a particularpoint in time during backing of the trailer by the vehicle.

In another embodiment of the present invention, a vehicle comprises atrailer angle detection apparatus and a trailer backup control system.The trailer angle detection apparatus is configured for outputting hitchangle information generated as a function of an angle between thevehicle and a trailer towably attached to the vehicle. The trailerbackup control system includes a jackknife enabling condition detectorand a jackknife counter-measures controller coupled to the trailer angledetection apparatus. The jackknife enabling condition detector iscoupled to the trailer angle detection apparatus for receiving the hitchangle information therefrom and for determining if a jackknife enablingcondition has been attained at a particular point in time during backingof the trailer by the vehicle. The jackknife counter-measures controllerimplements a vehicle speed reducing action in response to the jackknifeenabling condition detector determining that the jackknife enablingcondition has been attained at the particular point in time duringbacking of the trailer by the vehicle.

These and other objects, embodiments, advantages and/or distinctions ofthe present invention will become readily apparent upon further reviewof the following specification, associated drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a vehicle configured for performing trailer backup assistfunctionality in accordance with an embodiment of the present inventionembodiment.

FIG. 2 shows a preferred embodiment of the trailer backup steering inputapparatus discussed in reference to FIG. 1.

FIG. 3 shows an example of a trailer backup sequence implemented usingthe trailer backup steering input apparatus discussed in reference toFIG. 2.

FIG. 4 shows a method for implementing trailer backup assistfunctionality in accordance with an embodiment of the present invention.

FIG. 5 is a diagrammatic view showing a kinematic model configured forproviding information utilized in providing trailer backup assistfunctionality in accordance with the present invention.

FIG. 6 is a graph showing an example of a trailer path curvaturefunction plot for a rotary-type trailer backup steering input apparatusconfigured in accordance with the present invention.

FIG. 7 is a diagrammatic view showing a relationship between hitch angleand steered angle as it relates to determining a jackknife angle for avehicle/trailer system.

FIG. 8 shows a method for implementing jackknife countermeasuresfunctionality in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWING FIGURES

The present invention is directed to providing trailer backup assistfunctionality. In particular, such trailer backup assist functionalityis directed to implementing one or more vehicle speed reducing actionsfor limiting the potential for or alleviating a jackknife conditionbetween a vehicle and a trailer being towed by the vehicle. In certainembodiments of the present invention, curvature of a path of travel ofthe trailer (i.e., trailer path curvature control) can be controlled byallowing a driver of the vehicle to specify a desired path of thetrailer by inputting a desired trailer path curvature as the backupmaneuver of the vehicle and trailer progresses. Although a control knob,a set of virtual buttons, or a touch screen can each be implemented forenabling trailer path curvature control, the present invention is notunnecessarily limited to any particular configuration of interfacethrough which a desired trailer path curvature is inputted. Furthermore,in the case where a steering wheel can be mechanically decoupled fromsteered wheels of the vehicle, the steering wheel can also be used as aninterface through which a desired trailer path curvature is inputted. Aswill be discussed herein in greater detail, kinematical information of asystem defined by the vehicle and the trailer are used to calculate arelationship (i.e., kinematics) between the trailer's curvature and thesteering angle of the vehicle for determining steering angle changes ofthe vehicle for achieving the specified trailer path. Steering commandscorresponding to the steering angle changes are used for controlling asteering system of the vehicle (e.g., electric power assisted steering(EPAS) system) of the vehicle for implementing steering angle changes ofsteered wheels of the vehicle to achieve (e.g., to approximate) thespecified path of travel of the trailer.

Referring to FIG. 1, an embodiment of a vehicle 100 configured forperforming trailer backup assist functionality in accordance with thepresent invention is shown. A trailer backup assist system 105 of thevehicle 100 controls the curvature of path of travel of the trailer 110that is attached to the vehicle 100. Such control is accomplishedthrough interaction of a power assisted steering system 115 of thevehicle 100 and the trailer backup assist system 105. During operationof the trailer backup assist system 105 while the vehicle 100 is beingreversed, a driver of the vehicle 100 is sometimes limited in the mannerin which he/she can make steering inputs via a steering wheel of thevehicle 100. This is because in certain vehicles the trailer backupassist system 105 is in control of the power assisted steering system115 and the power assisted steering system 115 is directly coupled tothe steering wheel (i.e., the steering wheel of the vehicle 100 moves inconcert with steered wheels of the vehicle 100). As is discussed belowin greater detail, a human machine interface (HMI) of the backup assistsystem 105 is used for commanding changes in curvature of a path of thetrailer 110 such as a knob, thereby decoupling such commands from beingmade at the steering wheel of the vehicle 100. However, some vehiclesconfigured to provide trailer backup assist functionality in accordancewith the present invention will have the capability to selectivelydecouple steering movement from movement of steerable wheels of thevehicle, thereby allowing the steering wheel to be used for commandingchanges in curvature of a path of a trailer during such trailer backupassist.

The trailer backup assist system 105 includes a trailer backup assistcontrol module 120, a trailer backup steering input apparatus 125, and ahitch angle detecting apparatus 130. The trailer backup assist controlmodule 120 is connected to the trailer backup steering input apparatus125 and the hitch angle detecting apparatus 130 for allowingcommunication of information there between. It is disclosed herein thatthe trailer backup steering input apparatus can be coupled to thetrailer backup assist control module 120 in a wired or wireless manner.The trailer backup assist system control module 120 is attached to apower-steering assist control module 135 of the power-steering assistsystem 115 for allowing information to be communicated therebetween. Asteering angle detecting apparatus 140 of the power-steering assistsystem 115 is connected to the power-steering assist control module 125for providing information thereto. The trailer backup assist system isalso attached to a brake system control module 145 and a powertraincontrol module 150 for allowing communication of informationtherebetween. Jointly, the trailer backup assist system 105, thepower-steering assist system 115, the brake system control module 145,the powertrain control module 150 define a trailer backup assistarchitecture configured in accordance with an embodiment of the presentinvention.

The trailer backup assist control module 120 is configured forimplementing logic (i.e., instructions) for receiving information fromthe trailer backup steering input apparatus 125, the hitch angledetecting apparatus 130, the power-steering assist control module 135,the brake system control module 145, and the powertrain control module150. The trailer backup assist control module 120 (e.g., a trailercurvature algorithm thereof) generates vehicle steering information as afunction of all or a portion of the information received from thetrailer backup steering input apparatus 125, the hitch angle detectingapparatus 130, the power-steering assist control module 135, the brakesystem control module 145, and the powertrain control module 150.Thereafter, the vehicle steering information is provided to thepower-steering assist control module 135 for affecting steering of thevehicle 100 by the power-steering assist system 115 to achieve acommanded path of travel for the trailer 110.

The trailer backup steering input apparatus 125 provides the trailerbackup assist control module 120 with information defining the commandedpath of travel of the trailer 110 to the trailer backup assist controlmodule 120 (i.e., trailer steering information). The trailer steeringinformation can include information relating to a commanded change inthe path of travel (e.g., a change in radius of path curvature) andinformation relating to an indication that the trailer is to travelalong a path defined by a longitudinal centerline axis of the trailer(i.e., along a substantially straight path of travel). As will bediscussed below in detail, the trailer backup steering input apparatus125 preferably includes a rotational control input device for allowing adriver of the vehicle 100 to interface with the trailer backup steeringinput apparatus 125 to command desired trailer steering actions (e.g.,commanding a desired change in radius of the path of travel of thetrailer and/or commanding that the trailer travel along a substantiallystraight path of travel as defined by a longitudinal centerline axis ofthe trailer). In a preferred embodiment, the rotational control inputdevice is a knob rotatable about a rotational axis extending through atop surface/face of the knob. In other embodiments, the rotationalcontrol input device is a knob rotatable about a rotational axisextending substantially parallel to a top surface/face of the knob.

Some vehicles (e.g., those with active front steer) have apower-steering assist system configuration that allows a steering wheelto be decoupled from movement of the steered wheels of such a vehicle.Accordingly, the steering wheel can be rotated independent of the mannerin which the power-steering assist system of the vehicle controls thesteered wheels (e.g., as commanded by vehicle steering informationprovided by to a power-steering assist system control module from atrailer backup assist system control module configured in accordancewith an embodiment of the present invention). As such, in these types ofvehicles where the steering wheel can be selectively decoupled from thesteered wheels to allow independent operation thereof, trailer steeringinformation of a trailer backup assist system configured in accordancewith the present invention can be provided through rotation of thesteering wheel. Accordingly, it is disclosed herein that in certainembodiments of the present invention, the steering wheel is anembodiment of a rotational control input device in the context of thepresent invention. In such embodiments, the steering wheel would bebiased (e.g., by an apparatus that is selectively engagable/activatable)to an at-rest position between opposing rotational ranges of motion.

The hitch angle detecting apparatus 130, which operates in conjunctionwith a hitch angle detection component 155 of the trailer 110, providesthe trailer backup assist control module 120 with information relatingto an angle between the vehicle 100 and the trailer 110 (i.e., hitchangle information). In a preferred embodiment, the hitch angle detectingapparatus 130 is a camera-based apparatus such as, for example, anexisting rear view camera of the vehicle 100 that images (i.e., visuallymonitors) a target (i.e., the hitch angle detection component 155)attached the trailer 110 as the trailer 110 is being backed by thevehicle 100. Preferably, but not necessarily, the hitch angle detectioncomponent 155 is a dedicated component (e.g., an item attachedto/integral with a surface of the trailer 110 for the express purpose ofbeing recognized by the hitch angle detecting apparatus 130).Alternatively, the hitch angle detecting apparatus 130 can be a devicethat is physically mounted on a hitch component of the vehicle 100and/or a mating hitch component of the trailer 110 for determining anangle between centerline longitudinal axes of the vehicle 100 and thetrailer 110. The hitch angle detecting apparatus 130 can be configuredfor detecting a jackknife enabling condition and/or related information(e.g., when a hitch angle threshold has been met).

The power-steering assist control module 135 provides the trailer backupassist control module 120 with information relating to a rotationalposition (e.g., angle) of the steering wheel angle and/or a rotationalposition (e.g., turning angle(s)) of steered wheels of the vehicle 100.In certain embodiments of the present invention, the trailer backupassist control module 120 can be an integrated component of the powersteering assist system 115. For example, the power-steering assistcontrol module 135 can include a trailer back-up assist algorithm forgenerating vehicle steering information as a function of all or aportion of information received from the trailer backup steering inputapparatus 125, the hitch angle detecting apparatus 130, thepower-steering assist control module 135, the brake system controlmodule 145, and the powertrain control module 150.

The brake system control module 145 provides the trailer backup assistcontrol module 120 with information relating to vehicle speed. Suchvehicle speed information can be determined from individual wheel speedsas monitored by the brake system control module 145. In some instances,individual wheel speeds can also be used to determine a vehicle yawangle and/or yaw angle rate and such yaw angle and/or yaw angle rate canbe provided to the trailer backup assist control module 120 for use indetermining the vehicle steering information. In certain embodiments,the trailer backup assist control module 120 can provide vehicle brakinginformation to the brake system control module 145 for allowing thetrailer backup assist control module 120 to control braking of thevehicle 100 during backing of the trailer 110. For example, using thetrailer backup assist control module 120 to regulate speed of thevehicle 100 during backing of the trailer 110 can reduce the potentialfor unacceptable trailer backup conditions. Examples of unacceptabletrailer backup conditions include, but are not limited to, a vehicleoverspeed condition, trailer angle dynamic instability, a trailerjack-knife condition as defined by an angular displacement limitrelative to the vehicle 100 and the trailer 110, and the like. It isdisclosed herein that the backup assist control module 120 can issue asignal corresponding to a notification (e.g., a warning) of an actual,impending, and/or anticipated unacceptable trailer backup condition.

The powertrain control module 150 interacts with the trailer backupassist control module 120 for regulating speed and acceleration of thevehicle 100 during backing of the trailer 110. As mentioned above,regulation of the speed of the vehicle 100 is necessary to limit thepotential for unacceptable trailer backup conditions such as, forexample, jack-knifing and trailer angle dynamic instability. Similar tohigh-speed considerations as they relate to unacceptable trailer backupconditions, high acceleration can also lead to such unacceptable trailerbackup conditions.

Referring now to FIG. 2, a preferred embodiment of the trailer backupsteering input apparatus 125 discussed in reference to FIG. 1 is shown.A rotatable control element in the form of a knob 170 is coupled to amovement sensing device 175. The knob 170 is biased (e.g., by a springreturn) to an at-rest position P(AR) between opposing rotational rangesof motion R(R), R(L). A first one of the opposing rotational ranges ofmotion R(R) is substantially equal to a second one of the opposingrotational ranges of motion R(L), R(R). To provide a tactile indicationof an amount of rotation of the knob 170, a force that biases the knob170 toward the at-rest position P(AR) can increase (e.g., non-linearly)as a function of the amount of rotation of the knob 170 with respect tothe at-rest position P(AR). Additionally, the knob 170 can be configuredwith position indicating detents such that the driver can positivelyfeel the at-rest position P(AR) and feel the ends of the opposingrotational ranges of motion R(L), R(R) approaching (e.g., soft endstops).

The movement sensing device 175 is configured for sensing movement ofthe knob 170 and outputting a corresponding signal (i.e., movementsensing device signal) to the trailer assist backup input apparatus 125shown in FIG. 1. The movement sensing device signal is generated as afunction of an amount of rotation of the knob 170 with respect to theat-rest position P(AR), a rate movement of the knob 170, and/or adirection of movement of the knob 170 with respect to the at-restposition P(AR). As will be discussed below in greater detail, theat-rest position P(AR) of the knob 170 corresponds to a movement sensingdevice signal indicating that the vehicle 100 should be steered suchthat the trailer 100 is backed along a substantially straight path asdefined by a centerline longitudinal axis of the trailer 110 when theknob 170 was returned to the at-rest position P(AR) and a maximumclockwise and anti-clockwise position of the knob 170 (i.e., limits ofthe opposing rotational ranges of motion R(R), R(L)) each corresponds toa respective movement sensing device signal indicating a tightest radiusof curvature (i.e., most acute trajectory) of a path of travel of thetrailer 110 that is possible without the corresponding vehicle steeringinformation causing a jack-knife condition. In this regard, the at-restposition P(AR) is a zero curvature commanding position with respect tothe opposing rotational ranges of motion R(R), R(L). It is disclosedherein that a ratio of a commanded curvature of a path of a trailer(e.g., radius of a trailer trajectory) and a corresponding amount ofrotation of the knob can vary (e.g., non-linearly) over each one of theopposing rotational ranges of motion R(L), R(R) of the knob 170. It isalso disclosed therein that the ratio can be a function of vehiclespeed, trailer geometry, vehicle geometry, hitch geometry and/or trailerload.

Use of the knob 170 decouples trailer steering inputs from being made ata steering wheel of the vehicle 100. In use, as a driver of the vehicle100 backs the trailer 110, the driver can turn the knob 170 to dictate acurvature of a path of the trailer 110 to follow and returns the knob170 to the at-rest position P(AR) for causing the trailer 110 to bebacked along a straight line. Accordingly, in embodiments of trailerbackup assist systems where the steering wheel remains physicallycoupled to the steerable wheels of a vehicle during backup of anattached trailer, a rotatable control element configured in accordancewith the present invention (e.g., the knob 170) provides a simple anduser-friendly means of allowing a driver of a vehicle to input trailersteering commands.

It is disclosed herein that a rotational control input device configuredin accordance with embodiments of the present invention (e.g., the knob170 and associated movement sensing device) can omit a means for beingbiased to an at-rest position between opposing rotational ranges ofmotion. Lack of such biasing allows a current rotational position of therotational control input device to be maintained until the rotationalcontrol input device is manually moved to a different position.Preferably, but not necessarily, when such biasing is omitted, a meansis provided for indicating that the rotational control input device ispositioned in a zero curvature commanding position (e.g., at the sameposition as the at-rest position in embodiments where the rotationalcontrol input device is biased). Examples of means for indicating thatthe rotational control input device is positioned in the zero curvaturecommanding position include, but are not limited to, a detent that therotational control input device engages when in the zero curvaturecommanding position, a visual marking indicating that the rotationalcontrol input device is in the zero curvature commanding position, anactive vibratory signal indicating that the rotational control inputdevice is in or approaching the zero curvature commanding position, anaudible message indicating that the rotational control input device isapproaching the zero curvature commanding position, and the like.

It is also disclosed herein that embodiments of the present inventioncan be configured with a control input device that is not rotational(i.e., a non-rotational control input device). Similar to a rotationalcontrol input device configured in accordance with embodiments of thepresent invention (e.g., the knob 170 and associated movement sensingdevice), such a non-rotational control input device is configured toselectively provide a signal causing a trailer to follow a path oftravel segment that is substantially straight and to selectively providea signal causing the trailer to follow a path of travel segment that issubstantially curved. Examples of such a non-rotational control inputdevice include, but are not limited to, a plurality of depressiblebuttons (e.g., curve left, curve right, and travel straight), a touchscreen on which a driver traces or otherwise inputs a curvature for pathof travel commands, a button that is translatable along an axis forallowing a driver to input path of travel commands, and the like.

The trailer backup steering input apparatus 125 can be configured toprovide various feedback information to a driver of the vehicle 100.Examples of situation that such feedback information can indicateinclude, but are not limited to, a status of the trailer backup assistsystem 105 (e.g., active, in standby (e.g., when driving forward toreduce the trailer angle), faulted, inactive, etc), that a curvaturelimit has been reached (i.e., maximum commanded curvature of a path oftravel of the trailer 110), etc. To this end, the trailer backupsteering input apparatus 125 can be configured to provide a tactilefeedback signal (e.g., a vibration through the knob 170) as a warning ifany one of a variety of conditions occur. Examples of such conditionsinclude, but are not limited to, the trailer 110 having jack-knifed, thetrailer backup assist system 105 has had a failure, the trailer backupassist system 105 or other system of the vehicle 100 has predicted acollision on the present path of travel of the trailer 110, the trailerbackup system 105 has restricted a commanded curvature of a trailer'spath of travel (e.g., due to excessive speed or acceleration of thevehicle 100), and the like. Still further, it is disclosed that thetrailer backup steering input apparatus 125 can use illumination (e.g.,an LED 180) and/or an audible signal output (e.g., an audible outputdevice 185) to provide certain feedback information (e.g.,notification/warning of an unacceptable trailer backup condition).

Referring now to FIGS. 2 and 3, an example of using the trailer backupsteering input apparatus 125 for dictating a curvature of a path oftravel (POT) of a trailer (i.e., the trailer 110 shown in FIG. 1) whilebacking up the trailer with a vehicle (i.e., the vehicle 100 in FIGS. 1and 2) is shown. In preparation of backing the trailer 110, the driverof the vehicle 100 drives the vehicle 100 forward along a pull-thru path(PTP) to position the vehicle 100 and trailer 110 at a first backupposition B1. In the first backup position B1, the vehicle 100 andtrailer 110 are longitudinally aligned with each other such that alongitudinal centerline axis L1 of the vehicle 100 is aligned with(e.g., parallel with or coincidental with) a longitudinal centerlineaxis L2 of the trailer 110. It is disclosed herein that such alignmentof the longitudinal axes L1, L2 at the onset of an instance of trailerbackup functionality is not a requirement for operability of a trailerbackup assist system configured in accordance with the presentinvention.

After activating the trailer backup assist system 105 (e.g., before,after, or during the pull-thru sequence), the driver begins to back thetrailer 110 by reversing the vehicle 100 from the first backup positionB1. So long as the knob 170 of the trailer backup steering inputapparatus 125 remains in the at-rest position P(AR), the trailer backupassist system 105 will steer the vehicle 100 as necessary for causingthe trailer 110 to be backed along a substantially straight path oftravel as defined by the longitudinal centerline axis L2 of the trailer110 at the time when backing of the trailer 110 began. When the trailerreaches the second backup position B2, the driver rotates the knob 170to command the trailer 110 to be steered to the right (i.e., a knobposition R(R)). Accordingly, the trailer backup assist system 105 willsteer the vehicle 100 for causing the trailer 110 to be steered to theright as a function of an amount of rotation of the knob 170 withrespect to the at-rest position P(AR), a rate movement of the knob 170,and/or a direction of movement of the knob 170 with respect to theat-rest position P(AR). Similarly, the trailer 110 can be commanded tosteer to the left by rotating the knob 170 to the left. When the trailerreaches backup position B3, the driver allows the knob 170 to return tothe at-rest position P(AR) thereby causing the trailer backup assistsystem 105 to steer the vehicle 100 as necessary for causing the trailer110 to be backed along a substantially straight path of travel asdefined by the longitudinal centerline axis L2 of the trailer 110 at thetime when the knob 170 was returned to the at-rest position P(AR).Thereafter, the trailer backup assist system 105 steers the vehicle 100as necessary for causing the trailer 110 to be backed along thissubstantially straight path to the fourth backup position B4. In thisregard, arcuate (e.g., curved) portions of a path of travel POT of thetrailer 110 are dictated by rotation of the knob 170 and straightportions of the path of travel POT are dictated by an orientation of thecenterline longitudinal axis L2 of the trailer when the knob 170 isin/returned to the at-rest position P(AR).

FIG. 4 shows a method 200 for implementing trailer backup assistfunctionality in accordance with an embodiment of the present invention.In a preferred embodiment, the method 200 for implementing trailerbackup assist functionality can be carried out using the trailer backupassist architecture discussed above in reference to the vehicle 100 andtrailer 110 of FIG. 1. Accordingly, trailer steering information isprovided through use of a rotational control input device (e.g., theknob 170 discussed in reference to FIG. 2).

An operation 202 is performed for receiving a trailer backup assistrequest. Examples of receiving the trailer backup assist request includeactivating the trailer backup assist system and providing confirmationthat the vehicle and trailer are ready to be backed. After receiving atrailer backup assist request (i.e., while the vehicle is beingreversed), an operation 204 is performed for receiving a trailer backupinformation signal. Examples of information carried by the trailerbackup information signal include, but is not limited to, informationfrom the trailer backup steering input apparatus 125, information fromthe hitch angle detecting apparatus 130, information from thepower-steering assist control module 135, information from the brakesystem control module 145, and information from the powertrain controlmodule 150. It is disclosed herein that information from the trailerbackup steering input apparatus 125 preferably includes trailer pathcurvature information characterizing a desired curvature for the path oftravel of the trailer, such as provided by the trailer backup steeringinput apparatus 125 discussed above in reference to FIGS. 1 and 2. Inthis manner, the operation 204 for receiving the trailer backupinformation signal can include receiving trailer path curvatureinformation characterizing the desired curvature for the path of travelof the trailer.

If the trailer backup information signal indicates that a change incurvature of the trailer's path of travel is requested (i.e., commandedvia the knob 170), an operation 206 is performed for determining vehiclesteering information for providing the requested change in curvature ofthe trailer's path of travel. Otherwise, an operation 208 is performedfor determining vehicle steering information for maintaining a currentstraight-line heading of the trailer (i.e., as defined by thelongitudinal centerline axis of the trailer). Thereafter, an operation210 is performed for providing the vehicle steering information to apower-steering assist system of the vehicle, followed by an operation212 being performed for determining the trailer backup assist status. Ifit is determined that trailer backup is complete, an operation 214 isperformed for ending the current trailer backup assist instance.Otherwise the method 200 returns to the operation 204 for receivingtrailer backup information. Preferably, the operation for receiving thetrailer backup information signal, determining the vehicle steeringinformation, providing the vehicle steering information, and determiningthe trailer backup assist status are performed in a monitoring fashion(e.g., at a high rate of speed of a digital data processing device).Accordingly, unless it is determined that reversing of the vehicle forbacking the trailer is completed (e.g., due to the vehicle having beensuccessfully backed to a desired location during a trailer backup assistinstance, the vehicle having to be pulled forward to begin anothertrailer backup assist instance, etc), the method 200 will continually beperforming the operations for receiving the trailer backup informationsignal, determining the vehicle steering information, providing thevehicle steering information, and determining the trailer backup assiststatus.

It is disclosed herein that the operation 206 for determining vehiclesteering information for providing the requested change in curvature ofthe trailer's path of travel preferably includes determining vehiclesteering information as a function of trailer path curvature informationcontained within the trailer backup information signal. As will bediscussed below in greater detail, determining vehicle steeringinformation can be accomplished through a low order kinematic modeldefined by the vehicle and the trailer. Through such a model, arelationship between the trailer path curvature and commanded steeringangles of steered wheels of the vehicle can be generated for determiningsteering angle changes of the steered wheels for achieving a specifiedtrailer path curvature. In this manner, the operation 206 fordetermining vehicle steering information can be configured forgenerating information necessary for providing trailer path curvaturecontrol in accordance with the present invention.

In some embodiments of the present invention, the operation 210 forproviding the vehicle steering information to the power-steering assistsystem of the vehicle causes the steering system to generate acorresponding steering command as a function of the vehicle steeringinformation. The steering command is interpretable by the steeringsystem and is configured for causing the steering system to move steeredwheels of the steering system for achieving a steered angle as specifiedby the vehicle steering information. Alternatively, the steering commandcan be generated by a controller, module or computer external to thesteering system (e.g., a trailer backup assist control module) and beprovided to the steering system.

In parallel with performing the operations for receiving the trailerbackup information signal, determining the vehicle steering information,providing the vehicle steering information, and determining the trailerbackup assist status, the method 200 performs an operation 216 formonitoring the trailer backup information for determining if anunacceptable trailer backup condition exists. Examples of suchmonitoring include, but are not limited to assessing a hitch angle todetermine if a hitch angle threshold is exceeded, assessing a backupspeed to determine if a backup speed threshold is exceeded, assessingvehicle steering angle to determining if a vehicle steering anglethreshold is exceeded, assessing other operating parameters (e.g.,vehicle longitudinal acceleration, throttle pedal demand rate and hitchangle rate) for determining if a respective threshold value is exceeded,and the like. Backup speed can be determining from wheel speedinformation obtained from one or more wheel speed sensors of thevehicle. If it is determined that an unacceptable trailer backupcondition exists, an operation 218 is performed for causing the currentpath of travel of the trailer to be inhibited (e.g., stopping motion ofthe vehicle), followed by the operation 214 being performed for endingthe current trailer backup assist instance. It is disclosed herein thatprior to and/or in conjunction with causing the current trailer path tobe inhibited, one or more actions (e.g., operations) can be implementedfor providing the driver with feedback (e.g., a warning) that such anunacceptable trailer angle condition is impending or approaching. In oneexample, if such feedback results in the unacceptable trailer anglecondition being remedied prior to achieving a critical condition, themethod can continue with providing trailer backup assist functionalityin accordance with operations 204-212. Otherwise, the method can proceedto operation 214 for ending the current trailer backup assist instance.In conjunction with performing the operation 214 for ending the currenttrailer backup assist instance, an operation can be performed forcontrolling movement of the vehicle to correct or limit a jackknifecondition (e.g., steering the vehicle, decelerating the vehicle,limiting magnitude and/or rate of driver requested trailer curvatureinput, and/or the like to preclude the hitch angle from being exceeded).

Turning now to a discussion of a kinematic model used to calculate arelationship between a curvature of a path of travel of a trailer andthe steering angle of a vehicle towing the trailer, a low orderkinematic model can be desirable for a trailer back-up assist systemconfigured in accordance with some embodiments of the present invention.To achieve such a low order kinematic model, certain assumptions aremade with regard to parameters associated with the vehicle/trailersystem. Examples of such assumptions include, but are not limited to,the trailer being backed by the vehicle at a relatively low speed,wheels of the vehicle and the trailer having negligible (e.g., no) slip,tires of the vehicle, vehicle lateral compliance, and the trailer havingnegligible (e.g., no) deformation, actuator dynamics of the vehiclebeing negligible, the vehicle and the trailer exhibiting negligible(e.g., no) roll or pitch motions.

As shown in FIG. 5, for a system defined by a vehicle 302 and a trailer304, the kinematic model 300 is based on various parameters associatedwith the vehicle 302 and the trailer 304. These kinematic modelparameters include:

-   -   δ: steering angle at steered front wheels 306 of the vehicle        302;    -   α: yaw angle of the vehicle 302;    -   β: yaw angle of the trailer 304;    -   γ: hitch angle (γ=β−α);    -   W: wheel base of the vehicle 302;    -   L: length between hitch point 308 and rear axle 310 of the        vehicle 302;    -   D: length between hitch point 308 and axle 312 of the trailer        304; and    -   r₂: curvature radius for the trailer 304.

The kinematic model 300 of FIG. 5 reveals a relationship between trailerpath radius of curvature r₂ at the midpoint 314 of an axle 306 of thetrailer 304, steering angle δ of the steered wheels 306 of the vehicle302, and the hitch angle γ. As shown in the equation below, thisrelationship can be expressed to provide the trailer path curvature κ₂such that, if γ is given, the trailer path curvature κ₂ can becontrolled based on regulating the steering angle δ (where β(.) istrailer yaw rate and η(.) is trailer velocity).

$\kappa_{2} = {{\frac{1}{r_{2}}\frac{\overset{.}{\beta}}{\overset{.}{\eta}}} = \frac{{\left( {W + \frac{{KV}^{2}}{g}} \right)\sin \mspace{11mu} \gamma} + {L\mspace{11mu} \cos \mspace{11mu} \gamma \mspace{11mu} \tan \mspace{11mu} \delta}}{D\left( {{\left( {W + \frac{{KV}^{2}}{g}} \right)\cos \mspace{11mu} \gamma} - {L\mspace{11mu} \sin \mspace{11mu} \gamma \mspace{11mu} \tan \mspace{11mu} \delta}} \right)}}$

Or, this relationship can be expressed to provide the steering angle δas a function of trailer path curvature κ2 and hitch angle γ.

$\delta = {{\tan^{- 1}\left( \frac{\left( {W + \frac{{KV}^{2}}{g}} \right)\left\lbrack {{\kappa_{2}D\mspace{11mu} \cos \mspace{11mu} \gamma} - {\sin \mspace{11mu} \gamma}} \right\rbrack}{{{DL}\; \kappa_{2}\sin \mspace{11mu} \gamma} + {L\mspace{11mu} \cos \mspace{11mu} \gamma}} \right)} = {F\left( {\gamma,\kappa_{2},K} \right)}}$

Accordingly, for a particular vehicle and trailer combination, certainkinematic model parameters (e.g., D, W and L) are constant and assumedknown. V is the vehicle longitudinal speed and g is the acceleration dueto gravity. K is a speed dependent parameter which when set to zeromakes the calculation of steering angle independent of vehicle speed.For example, vehicle-specific kinematic model parameters can bepredefined in an electronic control system of a vehicle andtrailer-specific kinematic model parameters can be inputted by a driverof the vehicle. Trailer path curvature κ₂ is determined from the driverinput via a trailer backup steering input apparatus. Through the use ofthe equation for providing steering angle, a corresponding steeringcommand can be generated for controlling a steering system (e.g., anactuator thereof) of the vehicle.

FIG. 6 shows an example of a trailer path curvature function plot 400for a rotary-type trailer backup steering input apparatus (e.g., thetrailer backup steering input apparatus 125 discussed above in referenceto FIGS. 1 and 2). A value representing trailer path curvature (e.g.,trailer path curvature κ2) is provided as an output signal from therotary-type trailer backup steering input apparatus as a function ofuser input movement. In this example, a curve 402 specifying trailerpath curvature relative to user input (e.g., amount of rotation) at arotary input device (e.g., a knob) is defined by a cubic function.However, a skilled person will appreciate that embodiments of thepresent invention are not limited to any particular function between amagnitude and/or rate of input at a trailer backup steering inputapparatus (e.g., knob rotation) and a resulting trailer path curvaturevalue.

Referring to FIG. 5, in preferred embodiments of the present invention,it is desirable to limit the potential for the vehicle 302 and thetrailer 304 to attain a jackknife angle (i.e., the vehicle/trailersystem achieving a jackknife condition). A jackknife angle γ(j) refersto a hitch angle γ that cannot be overcome by the maximum steering inputfor a vehicle, when the vehicle is reversing, such as, for example, thesteered front wheels 306 of the vehicle 302 being moved to a maximumsteered angle δ at a maximum rate of steering angle change. Thejackknife angle γ(j) is a function of a maximum wheel angle for thesteered wheel 306 of the vehicle 302, the wheel base W of the vehicle302, the distance L between hitch point 308 and the rear axle 310 of thevehicle 302, and the length D between the hitch point 308 and the axle312 of the trailer 304. When the hitch angle γ for the vehicle 302 andthe trailer 304 achieves or exceeds the jackknife angle γ(j), thevehicle 302 must be pulled forward to reduce the hitch angle γ. Thus,for limiting the potential for a vehicle/trailer system attaining ajackknife angle, it is preferable to control the yaw angle of thetrailer while keeping the hitch angle of the vehicle/trailer systemrelatively small.

Referring to FIGS. 5 and 7, a steering angle limit for the steered frontwheels 306 requires that the hitch angle γ cannot exceed the jackknifeangle γ(j), which is also referred to as a critical hitch angle. Thus,under the limitation that the hitch angle γ cannot exceed the jackknifeangle γ(j), the jackknife angle γ(j) is the hitch angle γ that maintainsa circular motion for the vehicle/trailer system when the steered wheels306 are at a maximum steering angle δ(max). The steering angle forcircular motion with hitch angle is defined by the following equation.

${\tan \mspace{11mu} \delta_{\max}} = \frac{W\mspace{11mu} \sin \mspace{11mu} \gamma_{\max}}{D + {L\mspace{11mu} \cos \mspace{11mu} \gamma_{\max}}}$

Solving the above equation for hitch angle allows jackknife angle γ (j)to be determined. This solution, which is shown in the followingequation, can be used in implementing trailer backup assistfunctionality in accordance with the present invention for monitoringhitch angle in relation to jackknife angle.

${{\cos \overset{\_}{\gamma}} = \frac{{- b} \pm \sqrt{b^{2} - {4{ac}}}}{2a}},$

where,

a=L ² tan² δ(max)+W ²;

b=2 LD tan² δ(max); and

c=D ² tan² δ(max)−W ².

In certain instances of backing a trailer, a jackknife enablingcondition can arise based on current operating parameters of a vehiclein combination with a corresponding hitch angle. This condition can beindicated when one or more specified vehicle operating thresholds aremet while a particular hitch angle is present. For example, although theparticular hitch angle is not currently at the jackknife angle for thevehicle and attached trailer, certain vehicle operating parameters canlead to a rapid (e.g., uncontrolled) transition of the hitch angle tothe jackknife angle for a current commanded trailer path curvatureand/or can reduce an ability to steer the trailer away from thejackknife angle. One reason for a jackknife enabling condition is thattrailer curvature control mechanisms (e.g., those in accordance with thepresent invention) generally calculate steering commands at aninstantaneous point in time during backing of a trailer. However, thesecalculations will typically not account for lag in the steering controlsystem of the vehicle (e.g., lag in a steering EPAS controller). Anotherreason for the jackknife enabling condition is that trailer curvaturecontrol mechanisms generally exhibit reduced steering sensitivity and/oreffectiveness when the vehicle is at relatively high speeds and/or whenundergoing relatively high acceleration.

FIG. 8 shows a method 500 for implementing jackknife countermeasuresfunctionality in accordance with an embodiment of the present inventionfor a vehicle and attached trailer. Trailer backup assist functionalityin accordance with the present invention can include jackknifecountermeasures functionality. Alternatively, jackknife countermeasuresfunctionality in accordance with an embodiment of the present inventioncan be implemented separately from other aspects of trailer backupassist functionality.

The method 500 begins when operation 502 is performed for receivingjackknife determining information characterizing a jackknife enablingcondition of the vehicle-trailer combination at a particular point intime (e.g., at the point in time when the jackknife determininginformation was sampled). Examples of the jackknife determininginformation includes, but are not limited to, information characterizinga hitch angle, information characterizing a vehicle accelerator pedaltransient state, information characterizing a speed of the vehicle,information characterizing longitudinal acceleration of the vehicle,information characterizing a brake torque being applied by a brakesystem of the vehicle, information characterizing a powertrain torquebeing applied to driven wheels of the vehicle, and informationcharacterizing the magnitude and rate of driver requested trailercurvature. The operation 502 for receiving jackknife determininginformation can be the first operation in a sampling process wherejackknife determining information is sampled upon initiation of aninstance of implementing jackknife countermeasures functionality. Inthis regard, jackknife determining information would be continuallymonitored such as, for example, by a electronic control unit (ECU) thatcarries out trailer backup assist (TBA) functionality. As discussedabove in reference to FIG. 5, a kinematic model representation of thevehicle and the trailer can be used to determine a jackknife angle forthe vehicle-trailer combination. However, the present invention is notunnecessarily limited to any specific approach for determining thejackknife angle.

After receiving the jackknife determining information, an operation 504is performed for assessing the jackknife determining information fordetermining if the vehicle-trailer combination attained the jackknifeenabling condition at the particular point in time. The objective of theoperation 504 for assessing the jackknife determining information isdetermining if a jackknife enabling condition has been attained at thepoint in time defined by the jackknife determining information. If it isdetermined that a jackknife enabling condition is not present at theparticular point in time, the method 500 returns to the operation 502for receiving another instance of the jackknife determining information.If it is determined that a jackknife enabling condition is present atthe particular point in time, an operation 506 is performed fordetermining an applicable counter-measure or counter-measures toimplement. Accordingly, in some embodiments of the present invention, anapplicable counter-measure will be selected dependent upon a parameteridentified as being a key influencer of the jackknife enablingcondition. However, in other embodiments, an applicable counter-measurewill be selected as being most able to readily alleviate the jackknifeenabling condition. In still other embodiment, a pre-definedcounter-measure or pre-defined set of counter-measures may be theapplicable counter-measure(s).

The objective of a counter-measure in the context of the presentinvention (i.e., a jackknife reduction countermeasure) is to alleviate ajackknife enabling condition. To this end, such a counter-measure can beconfigured to alleviate the jackknife enabling condition using a varietyof different strategies. In a vehicle speed sensitive counter-measurestrategy, actions taken for alleviating the jackknife enabling conditioncan include overriding and/or limiting driver requested trailer radiusof curvature (e.g., being requested via a trailer backup steering inputapparatus configured in accordance with the present invention) as afunction of vehicle speed (e.g., via a look-up table correlating radiusof curvature limits to vehicle speed as shown in FIG. 6). In acounter-measure strategy where trailer curvature requests are limited asa function of speed and driver curvature command transient rates,actions taken for alleviating the jackknife enabling condition caninclude rate limiting trailer curvature command transients as requestedby a driver above a pre-defined vehicle speed whereas, under thepre-defined vehicle speed, the as-requested trailer curvature are notrate limited. In a torque limiting counter-measure strategy, actionstaken for alleviating the jackknife enabling condition can includeapplication of full available powertrain torque being inhibited when thejackknife enabling condition is present while the vehicle is above apre-defined speed and application of full available powertrain torquebeing allowed when the vehicle speed is reduced below the pre-definedspeed while in the torque inhibiting mode. As opposed to a fixedpre-defined speed, the torque limiting counter-measure strategy canutilize a speed threshold that is a function of hitch angle (i.e., speedthreshold inversely proportional to hitch angle acuteness). In a driveraccelerator pedal transient detection counter-measure strategy, actionstaken for alleviating the jackknife enabling condition can includeoverriding and/or limiting driver requested trailer radius of curvatureas a function of transient accelerator pedal requests (e.g., requestedtrailer radius of curvature limited when a large accelerator pedaltransient is detected). In a hitch angle rate sensitive counter-measurestrategy, actions taken for alleviating the jackknife enabling conditioncan include using hitch angle rate in a predefined or calculated mappingwith current hitch angle position to limit driver requested trailerradius of curvature. Accordingly, in view of the disclosures madeherein, a skilled person will appreciate that embodiments of the presentinvention are not unnecessarily limited to a counter-measure strategy ofany particular configuration.

As disclosed above, implementation of trailer backup assistfunctionality in accordance with the present invention can utilize akinematic model for determining steering control information, jackknifeenabling conditions, and jackknife angle. Such a kinematic model hasmany parameters than can influence trailer curvature controleffectiveness. Examples of these parameters include, but are not limitedto, the vehicle wheelbase, understeer gradient gain, vehicle trackwidth, maximum steer angle at the vehicle front wheels, minimum turningradius of vehicle, maximum steering rate able to be commanded by thesteering system, hitch ball to trailer axle length, and vehicle rearaxle to hitch ball length. Sensitivity analysis for a given kinematicmodel can be used to provide an understanding (e.g., sensitivity) of therelationships between such parameters, thereby providing informationnecessary for improving curvature control performance and for reducingthe potential for jackknife enabling conditions. For example, through anunderstanding of the sensitivity of the parameters of a kinematic model,scaling factors can be used with speed dependent jackknifecounter-measures to reduce jackknife potential (e.g., for specialapplications such as short wheelbase conditions).

Still referring to FIG. 8, after determining the applicablecountermeasure(s), an operation 508 is performed for implementing thechosen jackknife countermeasure(s) and an operation 510 is performed forinitiating a jackknife warning. As discussed above in regard tocounter-measure strategies, implementing the jackknifecounter-measure(s) can include commanding a speed controlling system ofthe vehicle to transition to an altered state of operation in which aspeed of the vehicle is reduced, commanding the steering control systemof the vehicle to transition to an altered state of operation in which aradius of a curvature of a path of the trailer is increased, command thesteering control system of the vehicle to transition to an altered stateof operation in which an increase in the radius of the curvature of thepath of the trailer is inhibited, commanding a brake control system ofthe vehicle to apply brake torque to reduce vehicle speed/inhibitvehicle acceleration, and/or commanding a powertrain control system ofthe vehicle to inhibit full available powertrain torque from beingdelivered to driven wheels of the vehicle until another jackknifeenabling parameter (e.g., vehicle speed) is below a defined threshold.In certain embodiments of the present invention, the jackknife warningis provided to the driver using at least one vehicle control systemthrough which the jackknife counter-measure is implemented. Speedreduction can be accomplished by any number of means such as, forexample, limiting throttle inputs (e.g., via a terrain managementfeature) and/or transitioning a transmission to a reverse low gear ifthe vehicle is equipped with a multi-range reverse gear transmission.Examples of such system-specific warning approach include, but are notlimited to, providing a warning through an accelerator pedal of thevehicle (e.g., via haptic feedback) if the counter-measure includeslimiting speed of the vehicle and/or providing a warning through aninput element (e.g., knob) of a trailer backup steering input apparatusof the vehicle (e.g., via haptic feedback if the counter-measureincludes limiting driver requested trailer radius of curvature), throughhaptic seat vibration warning, through a visual warning (e.g., a througha visual display apparatus of the towing vehicle) and/or through aaudible warnings (e.g., through an audio output apparatus of the towingvehicle), or the like.

One embodiment of utilizing warnings relating to vehicle speed as itrelated to onset or presence of a jackknife enabling condition includesimplementation of a dual stage warning. For example, when a backingspeed of the vehicle increases sufficiently for causing a speed of thevehicle to reach a lower (i.e., first) speed threshold during backing ofthe trailer, a driver of the vehicle would be provided with a firstwarning indication (e.g., via haptic, audible, and/or visual means asimplemented by the trailer backup assist system) for informing thedriver that there is the need to reduce the speed of the vehicle toalleviate or prelude the jackknife enabling condition. If the driverdoes not correspondingly respond by causing a speed of the vehicle to bereduced (or not to further increase) and the vehicle continues to gainspeed such that it passes a higher (i.e., a second) speed threshold, thedriver of the vehicle would be provided with a second warning indication(e.g., a more severed haptic, audible, and/or visual means asimplemented by the trailer backup assist system) for informing thedriver that there is an immediate need to reduce the speed of thevehicle to alleviate or prelude the jackknife enabling condition. Thefirst and/or the second speed indication warnings can be implemented inconjunction with a respective speed limiting counter-measure measures(e.g., the trailer backup assist system causing activation of a brakesystem of the vehicle and/or deducing a throttle position of thevehicle).

Referring now to instructions processible by a data processing device,it will be understood from the disclosures made herein that methods,processes and/or operations adapted for carrying out trailer backupassist functionality as disclosed herein are tangibly embodied bynon-transitory computer readable medium having instructions thereon thatare configured for carrying out such functionality. The instructions aretangibly embodied for carrying out the method 200 disclosed anddiscussed above and can be further configured for limiting the potentialfor a jackknife condition such as, for example, by monitoring jackknifeangle through use of the equations discussed in reference to FIGS. 5 and7 and/or by implementing jackknife countermeasures functionalitydiscussed above in reference to FIG. 8. The instructions may beaccessible by one or more data processing devices from a memoryapparatus (e.g. RAM, ROM, virtual memory, hard drive memory, etc), froman apparatus readable by a drive unit of a data processing system (e.g.,a diskette, a compact disk, a tape cartridge, etc) or both. Accordingly,embodiments of computer readable medium in accordance with the presentinvention include a compact disk, a hard drive, RAM or other type ofstorage apparatus that has imaged thereon a computer program (i.e.,instructions) configured for carrying out trailer backup assistfunctionality in accordance with the present invention.

In a preferred embodiment of the present invention, a trailer back-upassist control module (e.g., the trailer back-up assist control module120 discussed above in reference to FIG. 1) comprises such a dataprocessing device, such a non-transitory computer readable medium, andsuch instructions on the computer readable medium for carrying outtrailer backup assist functionality (e.g., in accordance with the method200 discussed above in reference to FIG. 2 and/or the method 500discussed above in reference to FIG. 8). To this end, the trailerback-up assist control module can comprise various signal interfaces forreceiving and outputting signals. For example, a jackknife enablingcondition detector can include a device providing hitch angleinformation and hitch angle calculating logic of the trailer back-upassist control module. A trailer back-up assist control module in thecontext of the present invention can be any control module of anelectronic control system that provides for trailer back-up assistcontrol functionality in accordance with the present invention.Furthermore, it is disclosed herein that such a control functionalitycan be implemented within a standalone control module (physically andlogically) or can be implemented logically within two or more separatebut interconnected control modules (e.g., of an electronic controlsystem of a vehicle) In one example, trailer back-up assist controlmodule in accordance with the present invention is implemented within astandalone controller unit that provides only trailer backup assistfunctionality. In another example, trailer backup assist functionalityin accordance with the present invention is implemented within astandalone controller unit of an electronic control system of a vehiclethat provides trailer backup assist functionality as well as one or moreother types of system control functionality of a vehicle (e.g.,anti-lock brake system functionality, steering power assistfunctionality, etc). In still another example, trailer backup assistfunctionality in accordance with the present invention is implementedlogically in a distributed manner whereby a plurality of control units,control modules, computers, or the like (e.g., an electronic controlsystem) jointly carry out operations for providing such trailer backupassist functionality.

In the preceding detailed description, reference has been made to theaccompanying drawings that form a part hereof, and in which are shown byway of illustration specific embodiments in which the present inventionmay be practiced. These embodiments, and certain variants thereof, havebeen described in sufficient detail to enable those skilled in the artto practice embodiments of the present invention. It is to be understoodthat other suitable embodiments may be utilized and that logical,mechanical, chemical and electrical changes may be made withoutdeparting from the spirit or scope of such inventive disclosures. Toavoid unnecessary detail, the description omits certain informationknown to those skilled in the art. The preceding detailed descriptionis, therefore, not intended to be limited to the specific forms setforth herein, but on the contrary, it is intended to cover suchalternatives, modifications, and equivalents, as can be reasonablyincluded within the spirit and scope of the appended claims.

1. A method, comprising: at least one data processing device accessing,from memory coupled to the at least one data processing device,instructions causing the at least one data processing device to assessjackknife determining information for a vehicle and a trailer towably tothe vehicle; and the at least one data processing device accessing, fromthe memory, instructions causing the at least one data processing deviceto implement a vehicle speed reducing action in response to thejackknife determining information indicating that a jackknife enablingcondition has been attained at a particular point in time during backingof the trailer by the vehicle.
 2. The method of claim 1 wherein causingthe at least one data processing device to implement the vehicle speedreducing action includes causing the at least one data processing deviceto alter at least one vehicle operating state of at least one vehicleoperating system capable of changing speed of the vehicle such that acurrent speed of the vehicle is reduced.
 3. The method of claim 2wherein the at least one vehicle operating system comprises at least oneof a vehicle operating system configured to control a position of athrottle of the vehicle and a vehicle operating system configured tocontrol actuation of brakes of the vehicle.
 4. The method of claim 1wherein causing the at least one data processing device to implement thevehicle speed reducing action includes at least one of causing aposition of a throttle of the vehicle to be decreased and causing brakesof the vehicle to be actuated.
 5. The method of claim 1 wherein causingthe at least one data processing device to implement the vehicle speedreducing action includes causing the at least one data processing deviceto: issue a first configuration of jackknife warning indication inresponse to a lower speed threshold being reached by the vehicle duringbacking of the trailer; and issue a second configuration of jackknifewarning indication in response to a speed of the vehicle furtherincreasing by a defined amount after the first configuration ofjackknife warning indication is issued.
 6. The method of claim 5wherein: causing the at least one data processing device to implementthe vehicle speed reducing action includes causing the at least one dataprocessing device to alter at least one vehicle operating state of atleast one vehicle operating system capable of changing speed of thevehicle such that a current speed of the vehicle is reduced; and causingthe at least one data processing device to alter the at least onevehicle operating state is performed in conjunction with causing the atleast one data processing device to issue the second configuration ofjackknife warning indication.
 7. The method of claim 6 wherein the atleast one vehicle operating system comprises at least one of a vehicleoperating system configured to control a position of a throttle of thevehicle and a vehicle operating system configured to control actuationof brakes of the vehicle.
 8. An electronic control system having a setof instructions tangibly embodied on a non-transitory processor-readablemedium thereof, the set of instructions are accessible from thenon-transitory processor-readable medium by at least one data processingdevice of the electronic controller system for being interpretedthereby, and the set of instructions is configured for causing the atleast one data processing device to carry out operations for: assessingjackknife determining information for a vehicle and a trailer towably tothe vehicle; and implementing a vehicle speed reducing action inresponse to the jackknife determining information indicating that ajackknife enabling condition has been attained at a particular point intime during backing of the trailer by the vehicle.
 9. The electroniccontrol system of claim 8 wherein implementing the vehicle speedreducing action includes altering at least one vehicle operating stateof at least one vehicle operating system capable of changing speed ofthe vehicle such that a current speed of the vehicle is reduced.
 10. Theelectronic control system of claim 9 wherein the at least one vehicleoperating system comprises at least one of a vehicle operating systemconfigured to control a position of a throttle of the vehicle and avehicle operating system configured to control actuation of brakes ofthe vehicle.
 11. The electronic control system of claim 8 whereinimplementing the vehicle speed reducing action includes at least one ofcausing a position of a throttle of the vehicle to be decreased andcausing brakes of the vehicle to be actuated.
 12. The electronic controlsystem of claim 8 wherein implementing the vehicle speed reducing actionincludes: issuing a first configuration of jackknife warning indicationin response to a lower speed threshold being reached by the vehicleduring backing of the trailer; and issuing a second configuration ofjackknife warning indication in response to a speed of the vehiclefurther increasing by a defined amount after the first configuration ofjackknife warning indication is issued.
 13. The electronic controlsystem of claim 12 wherein: implementing the vehicle speed reducingaction includes altering at least one vehicle operating state of atleast one vehicle operating system capable of changing speed of thevehicle such that a current speed of the vehicle is reduced; andaltering the at least one vehicle operating state is performed inconjunction with the second configuration of jackknife warningindication being issued.
 14. The electronic control system of claim 13wherein the at least one vehicle operating system comprises at least oneof a vehicle operating system configured to control a position of athrottle of the vehicle and a vehicle operating system configured tocontrol actuation of brakes of the vehicle.
 15. A vehicle, comprising: atrailer angle detection apparatus configured for outputting hitch angleinformation generated as a function of an angle between the vehicle anda trailer towably attached to the vehicle; a trailer backup controlsystem including a jackknife enabling condition detector and a jackknifecounter-measures controller coupled to the trailer angle detectionapparatus, wherein the jackknife enabling condition detector is coupledto the trailer angle detection apparatus for receiving the hitch angleinformation therefrom and for determining if a jackknife enablingcondition has been attained at a particular point in time during backingof the trailer by the vehicle, and wherein the jackknifecounter-measures controller implements a vehicle speed reducing actionin response to the jackknife enabling condition detector determiningthat the jackknife enabling condition has been attained at theparticular point in time during backing of the trailer by the vehicle.16. The vehicle of claim 15 wherein the vehicle speed reducing actionincludes altering at least one vehicle operating state of at least onevehicle operating system capable of changing speed of the vehicle suchthat a current speed of the vehicle is reduced.
 17. The vehicle of claim16 wherein the at least one vehicle operating system comprises at leastone of a vehicle operating system configured to control a position of athrottle of the vehicle and a vehicle operating system configured tocontrol actuation of brakes of the vehicle.
 18. The vehicle of claim 15wherein the vehicle speed reducing action includes at least one ofcausing a position of a throttle of the vehicle to be decreased andcausing brakes of the vehicle to be actuated.
 19. The vehicle of claim15 wherein the vehicle speed reducing action includes: issuing a firstconfiguration of jackknife warning indication in response to a lowerspeed threshold being reached by the vehicle during backing of thetrailer; and issuing a second configuration of jackknife warningindication in response to a speed of the vehicle further increasing by adefined amount after the first configuration of jackknife warningindication is issued.
 20. The vehicle of claim 19 wherein: implementingthe vehicle speed reducing action includes altering at least one vehicleoperating state of at least one vehicle operating system capable ofchanging speed of the vehicle such that a current speed of the vehicleis reduced; and altering the at least one vehicle operating state isperformed in conjunction with the second configuration of jackknifewarning indication being issued.